Many college students read science journal articles as a requisite for class and directed studies toward understanding experimental details. However, more often than not, most research endeavors involve a narrative about collaboration across several disciplines leading up to the discoveries published in journals.
In September 2012, professor Emery Bresnick and his research group in the Department of Cell and Regenerative Biology at the University of Wisconsin-Madison published a collaborative research article in the Journal of Clinical Investigation with Steven Holland, an expert in immunological diseases at the National Institute of Health (NIH), and Jing Zhang, an expert in blood cell development from the McArdle Laboratory for Cancer Research at UW-Madison.
This venture began with an intriguing colloquy between Holland and Bresnick about a DNA point mutation found near the Gata2 gene. This mutation was found in a DNA sequence of a patient with MonoMAC disease, a type of immunodeficiency disease that commonly progresses to leukemia.
Even though Bresnick’s research lab does not directly study immunodeficiency diseases like Holland’s lab, Bresnick’s research does study the physiological consequences from genetic mutations in genes regulating red blood cell development. Examples of these consequences include myeloid leukemia and poor vasculature integrity. One of the many genes involved in regulating red blood cell development is Gata2, a gene in the human genome that encodes for a protein called GATA-2.
Bresnick’s lab uses genetically modified mice to help elucidate the complicated network of Gata2 gene regulation in hematopoiesis.
“If this protein is missing or limiting, then the mouse embryo would die due to lack of red blood cells,” Bresnick said.
GATA-2 protein is a master regulator protein that helps control the blood cell maturation process in hematopoiesis, a common physiological development pathway of erythrocyte and leukocyte cells from hematopoietic stem cells. Research from various groups has demonstrated that the hematopoietic stem cells start with a high GATA-2 protein concentration.
Bresnick’s team mapped where the GATA-2 protein attaches to the chromosomal DNA. Consequently, they discovered that as the stem cell matures into a red blood cell by certain chemical growth factors, GATA-2 protein is switched with GATA-1 protein, a related regulatory protein, at the same site on the chromosomal DNA. This mechanism is called the “GATA switch.”
“When GATA-1 levels rise, it replaces GATA-2,” Bresnick said. “When it does that, it changes the activity of the associated gene.”
By using molecular techniques, Bresnick and his team found five GATA switch sites scattered within and upstream of the Gata2 gene.
“One [site] was in an intron of the Gata2 gene,” said Bresnick. “Three sites were immediately to the left of the gene and an additional site was very far upstream of the Gata2 gene.”
Bresnick said there were four papers published in 2011, which announced “point mutations, or a single amino acid change, occur in GATA-2 modifying the protein and not the +9.5 DNA regulatory sequence.” These mutations occur in individuals who have the immunodeficiency disease MonoMAC.
MonoMAC stands for monocytopenia and mycobacterial infection syndrome, which is a deficiency in dendritic, monocyte, B cells and Natural Killer cells. Since these types of white blood cells are part of the immune system, patients with MonoMAC are susceptible to mycobacterial, fungal and viral infections as well as human papillomavirus-associated cancers.
However, in one of Holland’s patients who had developed MonoMAC, the patient’s GATA-2 protein did not display any amino acid mutations as stated in the 2011 papers.
In pursuit of this genetic conundrum, Bresnick said Holland had read the research done by Bresnick’s lab and was curious if there was any application of Bresnick’s research to his patient who had MonoMAC disease with non-mutated GATA-2 protein. Thus, Holland had his staff member sequence the patient’s DNA and evaluate the integrity of the GATA-2 protein switch sites.
“Holland’s group identified a small deletion within the intron site, which corresponded to the +9.5 element,” Bresnick said.
The +9.5 site is one of the GATA-2 binding sites Bresnick’s lab had previously found in the intron of the Gata2 gene.
In addition to Holland’s contribution, Kirby Johnson, a senior scientist in the Bresnick group, made seminal contributions to all aspects of the study. Myung-Jeom Ryu, Jinyong Wang, Yangang Liu and Jing Zhang from the McArdle Laboratory for Cancer Research provided outstanding expertise to quantitate stem cell activity in the +9.5 site mutant animals generated in the Bresnick group.
“This long term study came to fruition through a highly productive multidisciplinary effort,” said Bresnick.
